Answer:
história phkfk
Explanation:
guiooupigjdytrss
Using Hess’s law, what is the standard enthalpy of formation of manganese (II) oxide, MnO(s)?
With the help of hess's law:
ΔHf(MnO)=−248.9 kJ−12(272.0) kJ=−384.9 kJ(per mole) Δ H f ( M n O ) = − 248.9 k J − 1 2 ( 272.0 ) k J = − 384.9 k J ( p e r m o l e )
What is Hess's law?Hess's law of constant heat summation, also known simply as Hess' law, is a relationship in physical chemistry named after Germain Hess, a Swiss-born Russian chemist and physician who published it in 1840.
Moreover, hess's Law of Constant Heat Summation (or just Hess's Law) states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes.
Therefore, hess' law is based on the state function character of enthalpy and the first law of thermodynamics. Energy (enthalpy) of a system (molecule) is a state function.
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The rate of the reaction is 1.6*10-2 M/s when the concentration of A is 0.15 M. Calculate the rate constant if the reaction is (a) first order in A and (b) second order in A.
Answer:
[tex]k_1=0.107s^{-1} \\\\k_2=0.711M^{-1}s^{-1}[/tex]
Explanation:
Hello there!
In this case, according to the given information and the attached picture in which we can see the units of the rate constant, it turns out possible for us to realize the two called rate laws are:
[tex]r=k[A]\\\\r=k[A]^2[/tex]
The former is first-order and the latter second-order; in such a way, we solve for the rate constant in both cases to obtain the following:
[tex]k=\frac{r}{[A]}=\frac{1.6x10^{-2}M/s}{0.15M}=0.107s^{-1} \\\\k=\frac{r}{[A]^2}=\frac{1.6x10^{-2}M/s}{(0.15M)^2}=0.711M^{-1}s^{-1}[/tex]
Regards!
The half life for the radioactive decay of potassium-40 to argon-40 is 1.26×109 years. Suppose nuclear chemical analysis shows that there is 0.359 mmol of argon-40 for every 1.000mmol of potassium-40 in a sample of rock. Calculate the age of the rock.
Answer:
2.42x10⁹ years is the age of the rock
Explanation:
The decay of an isotope follows the equation:
Ln[A] = -kt + Ln[A]₀
Where [A] is amount of isotope after time t, k is decay constant and [A]₀ is the initial amount of the isotope
To find decay constant from half-life:
k = ln2 / half-life
k = ln2 / 1.26x10⁹years
k = 5.501x10⁻¹⁰ years⁻¹
As in the reaction, K-40 produce Ar-40:
[A] = 0.359mmol
[A]₀ = 0.359mmol + 1.000mmol = 1.359mmol
Replacing:
Ln[0.359mmol] = -5.501x10⁻¹⁰ years⁻¹t + Ln[1.359mmol]
-1.3312 = -5.501x10⁻¹⁰ years⁻¹t
t = 2.42x10⁹ years is the age of the rock
How is the atomic mass of an element calculated?
Answer:
Mass number (A) is the number of nucleons (proton and neutron) present in a atom.
Explanation:
electrons don't cout since they are thousandth's of the mass of protons or neutrons
One mole of
C
2
H
6
O
C
2
H
6
O has two moles of Carbon (C), six moles of Hydrogen (H) and one mole of Oxygen (O). How many moles of Hydrogen is in 0.2 moles of
C
2
H
6
O
C
2
H
6
O?
Answer:
c
no need to thank me okay
Using a mole ratio, find the moles of Cu. You have been given the following
balanced chemical equation, and you have 1.5 moles of Al to start.*
2AI
+
3Cu(SO4)
3Cu
+
Al2(SO4)3n
n 1.5 moles
Answer: 2,25 mol
Explanation: 2Al + 3CuSO4 → Al2(SO4)3 + 3Cu
1,5 mol (1,5*3)/2 mol = 2,25 mol
A solution is formed by dissolving 83.2 grams of copper II chloride (CuCl2) in 2.5 liters of water. The molar mass of CuCl2 is 134.45 g/mol.
What is the molarity of the solution?
Explanation:
the answer is in the above image
0.159 mol 2.25 M = A L of HCI
Answer:
hmmm?what?
Explanation:
ayusin mo flece:>
Fabric A is used to rub a wooden rod. A second piece of Fabric A is used to rub an ebonite rod. It is observed that the wooden rod and the ebonite rod attract one another. What can you say about the position of Fabric A in the electrostatic series in relation to wood and ebonite?
Fabric A is likely to be a material that has a moderate tendency to gain electrons when in contact with other materials and is lower in the electrostatic series than ebonite but higher than wood.
What is electrostatic series?The electrostatic series is a list of materials ranked in order of their tendency to gain or lose electrons when in contact with another material.
Materials higher in the series tend to lose electrons more readily and become positively charged, while materials lower in the series tend to gain electrons more readily and become negatively charged.
Ebonite is a synthetic polymer that is known to become negatively charged when rubbed, and it is typically placed near the top of the electrostatic series.
Wood, on the other hand, is a poor conductor of electricity and does not readily become charged when rubbed. Based on these facts, we can infer that Fabric A is lower in the electrostatic series than ebonite, but higher than wood.
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The acid dissociation constant, Ka, of HNO3 is 4.0 x104. What does the ka
value indicate about this compound?
A. HNO3 is neither an acid nor a base,
B. HNO3 is a strong acid.
C. HNO3 is a weak acid
D. HNO3 is a strong base.
Answer:
i thing its b
Explanation:
The acid dissociation constant (Ka) is a measure of the strength of an acid in solution. In HNO₃ (nitric acid), the given Ka value is 4.0 x 10⁴. It represents the equilibrium constant for the dissociation reaction of an acid in water. Therefore, option B is correct.
The dissociation constant often denoted as Kd, is a measure of the strength of the interaction between a ligand and a receptor or between a substrate and an enzyme.
A high Ka value indicates a strong acid, while a low Ka value indicates a weak acid. In this case, the Ka value of 4.0 x 10⁴ for HNO₃ is relatively high.
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what is the scientific name of lion
Answer:
the scientific name of lion is
Panthera leo
examples of isotones
Answer:
Examples of isotones include carbon-12, nitrogen-13 and oxygen-14. These atoms all have six neutrons and six, seven and eight protons respectively. A mnemonic that can be used to differentiate isotones from isotopes and isobars is as follows: same Z (number of protons) = isotopes.
A chemist requires a large amount of 1-bromo-4-phenyl-2-butene as starting material for a synthesis and decides to carry out the following NBS allylic bromination reaction in the presence of UV light. Draw the structures of all of the observed products.
NBS
(C6H5)CH2CH = CHCH3 → ?
CCI4
Draw one additional resonance structure for the species below:
CH3CH=CHCH=CHCH=CHCH2
Answer:
CH 2 CH 3 CHCH = C6H5 + 5 Hydrogen Atoms
I hope I helped you.
Deepest apologies if I was wrong!
Bye!
~ Myaka O.
if 7.90 mol of C5H12 reacts with excess O2, how many moles of CO2 will be produced by the following combustion reaction?
Answer:
If 7.9 moles of C₅H₁₂ reacts with excess O₂, 39.5 moles of CO₂ will be produced.
Explanation:
The balanced reaction is:
C₅H₁₂ + 8 O₂ → 5 CO₂ + 6 H₂O
By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of moles of each compound participate in the reaction:
C₅H₁₂: 1 moles O₂: 8 molesCO₂: 5 moles H₂O: 6 molesThen you can apply the following rule of three: if by stoichiometry 1 mole of C₅H₁₂ produces 5 moles of CO₂, then 7.9 moles of C₅H₁₂ will produce how many moles of CO₂?
[tex]amount of moles of CO_{2} =\frac{7.9 moles of C_{5}H_{12}*5 moles of CO_{2} }{1 mole of C_{5}H_{12} }[/tex]
amount of moles of CO₂= 39.5 moles
If 7.9 moles of C₅H₁₂ reacts with excess O₂, 39.5 moles of CO₂ will be produced.
Nuclear reactions take place inside the nucleus of the atom. Which of the following does NOT represent an everyday example of a nuclear reaction?
Conversion of carbon dioxide and water in photosynthesis
Hydrogen atoms fused together in the Sun
Loss of protons and electrons in plutonium-240 decay
Energy produced by the Sun that is transferred to Earth
Answer:
Loss of protons and electrons in plutonium 240 decay is not an example of an everyday reaction
Describe why corrosion is a natural process
Answer :
Answer :because it happens due to moisture and oxygenDraw the product formed when diene and dienophile react in a Diels–Alder reaction.
Answer:
Explanation:
Diels-Alder reactions are cyclo-additional reactions between conjugated dienes and a dienophile (a substituted alkene compound for example acrylic acid) to produce a ring structure of cyclohexene compounds.
From the image attached below, we will see the reaction between 2,3-dimethylbuta-1,3-diene which is a conjugated diene with acrylic acid to produce a Diel-Alder adduct as the product. From the reaction, a single new π-bond and two σ-bonds are produced.
The products in a decomposition reaction _____. are compounds can be elements or compounds are elements include an element and a compound
Answer:
compounds are elements include an element and a compound
Explanation:
elements in the decomposition reaction is the substance that cannot be separated into simpler substances. Compounds, technically act as a reactant in the decomposition reaction, but since the reaction breakdown one substance into two or more, sometimes it exists in the product
Which of the following reasons explains why if salt water is heated, the water turns into steam while the salt remains?
Water and salt have an equal boiling point.
Water has a lower boiling point than salt.
Salt has a lower boiling point than water.
Salt and water have an equal melting point.
If the salt water is heated, the water turns into steam and the salt remains because the water has a lower boiling point than the salt.
The following points can be considered:
The boiling point is defined as the temperature at which the substance turns into the gaseous state from the liquid state.The boiling point of water is [tex]100^{o} C[/tex].The salt is a substance comprising two entities separated by the opposite charges with ionic interactions.The boiling point of a salt is higher than the boiling point of the water.The process involved when salt water is heated:
The salt water mixture when heated, the water turns into steam at [tex]100^{o} C[/tex]But the salt remains until it reaches its boiling temperature. If the salt is soluble in water and is then heated, then there occurs an elevation in the boiling point of the substance, due to the presence of the salt.Therefore, the answer is water has a lower boiling point than salt.
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When stirred in 30°C water, 5 g of powdered potassium bromide, KBr, dissolves faster than 5 g of large crystals of potassium bromide. Which of the following best explains why the powdered KBr dissolves faster?
A. Potassium ions and bromide ions in the powder are smaller than potassium ions and bromide ions in the large crystals.
B. Powdered potassium bromide exposes more surface area to water molecules than large crystals of potassium bromide.
C. Fewer potassium ions and bromide ions have been separated from each other in the powder than in the crystals.
D. Powdered potassium bromide is less dense than large crystals of potassium bromide.
Answer:
B
Explanation:
Do diện tích tiếp xúc ở dạng bột cao hơn dạng tinh thể
PLZZZ HELPPPPPPPPPPPPPPPP
A student measures her computer keyboard with a meter stick and finds that it has a width of 47.35 cm. Which statement about this measurement is true?
PLZZZZ HELP
A.) All the numbers are certain
B.) The 4 is uncertain
C.) The 5 is somewhat uncertain
D.) The 5 is certain
How many grams of solid sodium cyanide should be added to 1.00 L of a 0.119 M hydrocyanic acid solution to prepare a buffer with a pH of 8.809
Answer:
1.62 g
Explanation:
Given that:
Concentration of HCN = 0.119 M
Assuming the ka 4.00 × 10⁻¹⁰
The pKa of HCN (hydrocyanic acid) = -log (Ka)
= - log ( 4.00 × 10⁻¹⁰)
= 9.398
pH of buffer = 8.809
Using Henderson Hasselbach equation:
[tex]pH = pKa + log \dfrac{[conjugate\ base ]}{acid}[/tex]
[tex]pH = pKa + log \dfrac{[CN^-]}{[HCN]}[/tex]
[tex]8.809 = 9.398 +log \dfrac{[CN^-]}{[HCN]}[/tex]
[tex]log \dfrac{[CN^-]}{[HCN]}= 8.809 - 9.398[/tex]
[tex]log \dfrac{[CN^-]}{[HCN]}= -0.589[/tex]
[tex]\dfrac{[CN^-]}{[HCN]}= 0.2576[/tex]
[CN^-] = 0.2576[HCN]
[CN^-] = 0.2756 (0.119) L
[CN^-] = 0.033 M
∴
The amount of NaCN (sodium cyanide) is calculated as follows:
[tex]= 1.00 L \times \dfrac{0.033 \ mol \ NacN }{1 \ L } \times \dfrac{49.01 \ g}{1 \ mol \ of \ NacN}[/tex]
= 1.62 g
What is nitrogen???? explain!!!
Answer:
It is a colourless, odourless, tasteless gas that is the most plentiful element in Earth's atmosphere and is a constituent of all living matter.
Explanation:
Have a nice day :D
Answer:
Nitrogen is a gas
Explanation:
Hukkam aap bio image dekhona please and bataona ki kese lage
Hey what is your guyses fear, I am terrified of wasp, especially those huge red ones I call red goobers.
Draw the predominant product(s) of the following reactions including stereochemistry when it is appropriate. CH3CH2 C C CH3 H2O/H2SO4/HgSO4
Answer:
Draw the predominant product(s) of the following reactions including stereochemistry when it is appropriate.
CH3CH2 C C CH3 H2O/H2SO4/HgSO4
Explanation:
The given compound is: pent-2-yne.
When it reacts with water, in presence of sulphuric acid and mercuric sulphate then a ketone is formed as shown below:
This reaction is an example of nucleophilic attack of water on carbon carbon triple bond.
The general mechanism of the reaction is hsown below:
Pent-2-yne reacts with water and form 3-pentanone.
The reaction is shown below:
Question 11
1 pts
A solution is formed by dissolving 45 grams of NH4Cl in
100 grams of H20 at 70°C. Which statement correctly
describes this solution?
O NH4Cl is the solute, and the solution is saturated.
O NH4Cl is the solute, and the solution is unsaturated.
o NH4Cl is the solvent, and the solution is unsaturated.
O NH4Cl is the solvent, and the solution is saturated.
< Previous
Answer:
NH4Cl is the solute, and the solution is unsaturated.
Explanation:
To create a saturated solution of ammonium chloride at 70°C, we need to dissolve 62 g of ammonium chloride in 100 g of water.
The question tells us that 45 grams of NH4Cl was dissolved in 100 grams of H20 at 70°C. This creates an unsaturated solution since the amount of solute present is less than the amount of solute that the NH4Cl solution can normally hold at 70°C.
Hence, NH4Cl is the solute, and the solution is unsaturated.
A steel with a critical fracture toughness of 150 MPa.m1/2 has a yield strength of 1500 MPa. If fracture were to take place at the yield stress, answer the following questions.
Surface crack size at yielding leading to failure is:_____________.
a. 0.497 cm
b. 0.994 cm
c. 0.32 cm
Answer:
c.
Explanation:
From the given information:
Critical fracture toughness [tex]K_{IC}[/tex] = 150 MPa.[tex]m ^{1/2}[/tex]
yield strength [tex]\sigma[/tex] = 1500 MPa
surface crack size [tex]a_c[/tex] = ???
The formula for the fracture toughness is can be expressed as:
[tex]K_{IC}= \sigma \sqrt{\pi a_c}[/tex]
replacing our values to solve for the surface crack size, we have:
[tex]150= 1500 \sqrt{\pi a_c}[/tex]
[tex]\dfrac{150}{ 1500} = \sqrt{\pi a_c}[/tex]
[tex]\dfrac{0.1}{1.77} = \sqrt{ a_c}[/tex]
[tex]a_c[/tex] = 0.0564²
[tex]a_c[/tex] = 0.0032 m
[tex]a_c[/tex] = 0.32 cm
A student collecting CaCO3 produced by the reaction of Na2CO3(aq) and CaCl2(aq) obtains a percent yield of 81%. Choose all of the following observations that could explain the low yield.
a. The combined reactants were not stirred before filtering the precipitate.
b. The student did not completely dry the precipitate before weighing it.
c. The precipitate was not washed prior to drying.
d. A rubber policeman was not used to scrape precipitate from the beaker.
e. The filter paper was not wetted with water prior to filtering the precipitate.
Answer:
a, d and e. are true.
Explanation:
The reaction that occurs is:
Na2CO3(aq) + CaCl2(aq) → CaCO3(s) + 2NaCl
In ideal conditions, the percent yield of the reaction must be 100%. All explanations about why the student could not collect all precipitate are right:
a. The combined reactants were not stirred before filtering the precipitate. Not stirring could not promote all the reaction. TRUE.
b. The student did not completely dry the precipitate before weighing it. If the student don't dry the precipitate, the mass of precipitate must be higher producing a percent yield > 100%. FALSE.
c. The precipitate was not washed prior to drying. Produce more mass. FALSE.
d. A rubber policeman was not used to scrape precipitate from the beaker. If the student doesn't collect all the precipitate the percent yield could be < 100%.. TRUE.
e. The filter paper was not wetted with water prior to filtering the precipitate. TRUE. If you don't wet the filter paper you can lose a part of precipitate from the walls of this one.
During a reaction in an aqueous solution, the concentration of bactants
decreases and the amount of products increases. How do these changes in
concentration affect the reaction rate?
A. The reaction rate decreases.
B. The reaction rate varies unpredictably.
C. The reaction rate increases.
D. The reaction rate stays the same.
Answer:
my define it will be turst me is c
